This invention relates to microchannel plate tubes such as image intensifiers and photomultipliers.
FIG. 1 of the article "Miniature imaging photon detectors" (J. Phys. E. Sci. Instrum., Vol. 13, 1980, Great Britain) discloses an arrangement where the photocathode appears on the input of a microchannel plate. However, no cathode is shown on the input window of the imaging photon device. In fact, FIG. 1 teaches away from having a cathode on the input window since the dimensions shown therein are such that focusing a light beam on the input window would cause it to be out of focus at the microchannel plate, and vice versa. FIG. 4 of this article and FIG. 1 of the article "Miniature imaging photon detectors II. Devices with transparent photocathodes" (J. Phys. E. Sci. Instrum., Vol. 14, 1981, Great Britain) show the same basic arrangement, and would have the same focusing problems even if a photo cathode were contemplated on the input window of the imaging photon detectors. The article "Miniature imaging photon detectors III. An assessment of the performance of the resistive anode IPD" (J. Phys. E. Sci. Instrum., Vol. 15, 1982, Great Britain) performance of the resistive anode IPD" further discusses the photon detectors in the aforementioned two articles.
U.S. Pat. No. 4,339,659, issued July 13, 1982, to C. B. Johnson, the inventor of the subject invention, discloses an image converter wherein radiant energy passes through a window to impinge on a photocathode which is formed on a radiant energy sensitive phosphor that is in turn deposited on the input electrode of a microchannel plate. However, there is no statement or suggestion in the patent of having a photocathode on the input window.
Well known in the art are microchannel plate tubes with a photocathode on the tube input window. However, such tubes do not have an additional photocathode placed on the microchannel plate input.